Most oil wells require that a pumping unit of some sort be employed in order to lift hydrocarbons from the bottom of the borehole up to the surface of the ground. This pumping action is usually accomplished by employment of a pumpjack unit having a prime mover which drives a gear box, which in turn rocks a walking beam. A horsehead attached to the end of the walking beam receives a pair of cables which comprises a bridle. It is customary to directly attach a polished rod to the bridle to enable a wellhead packiny gland to sealingly engage the polished rod and seal the upper end of a production string through which the produced oil is pumped. A string of sucker rod extends from the polished rod, several thousand feet downhole to a production pump. The production pump is therefore reciprocated by the sucker rod string, which in turn is reciprocated by the polished rod of the pumpjack unit.
One of the major costs in producing an oil well is the maintenance of a pumpjack unit. Sucker rods often fail because of rod parting. This requires that an expensive pulling unit be moved onto location to remove the rod and the pump from the borehole, and replace the several throusand feet of sucker rod with new or rebuilt rod material. There are many different explanations and many proposed solutions to overcome the costly failure of sucker rods; but nevertheless, reduction of sucker rod failure appears to be one of the principal needs for the economic production of oil wells at their full capacity.
As a pumpjack unit reciprocates the downhole pump, the sucker rod string is subjected to a peak load on the up-stroke and on the down-stroke. The peak determines the size of the rod string, and therefore indirectly determines the pump size as well as the pumping speed.
It would therefore be desirable to be able to dampen or somehow reduce the peak load imparted into the rod string so as to reduce the maximum strain on the rod string. Such a desirable phenomenon would reduce the cold working stresses imposed upon the rod, enable fastener pumping speeds, and elongate the life expectancy of the expensive pumping unit as well as the downhole pump, all of which would tend to reduce the cost of producing the oil well. Such a desirable apparatus is the subject of this invention.